Technical Abstract:
The rising cost of inorganic commercial fertilizer has renewed interest in introducing legumes into paddocks of tame grass. Legumes fix atmospheric nitrogen (N), which will be available to the legume and some will be available to the following non-legume crop, reducing the need for N fertilizers (Badaruddin and Mayer, 1994; Rao et al., 2005). Inter-seeding legumes into paddocks of tame grasses can improve forage quality by supplying high N biomass. Legumes generally have greater relative feed value than warm-season grasses (Petritz et al., 1980). Grasspea (Lathyrus sativus L. cv. AC Greenfix), also known as chickling vetch, is a cool-season annual pulse known for its tolerance to dry conditions and adaptability to difficult environments. Proper agronomic practices are necessary to maximize the yield of grass pea. We examined the influence of planting dates (March 15, April 01 and April 15) on yield and nutritive values of grasspea in the southern Great Plains. Planting date effect on biomass yield was minimal, though nitrogen accumulation varied among planting dates. At peak production, N accumulation was 135, 153, and 125 kg N ha-1, respectively for 15 March, 01 April, and 15 April planting dates. Studies also tested the effect of inter-seeding cool-season pulses such as Grasspea and Lentils (Lens culinaris Med.) into bermudagrass [Cynodon dactylon (L.) Pers.] – a warm-season perennial - paddocks to reduce N inputs. The objective was to compare forage yield and nutritive value of inter-seeded stands with pure stands of bermudagrass receiving three levels of N fertilizer (0, 45 and 90 kg N ha-1). Total end-of-season standing dry matter of bermudagrass and inter-seeded grasspea was 5550 ± 423 (SEM) kg ha-1, which was similar to biomass production of bermudagrass paddocks receiving 45 kg N ha-1 (5305 ± 570 kg ha-1 (Fig. 1). Seeding grasspea or lentil into bermudagrass resulted in large improvements in quality and total herbage. Seeding grasspea into bermudagrass paddocks allowed the quality of forage to exceed that of plant materials produced with 90 kg N ha-1 of applied fertilizer, while inter-seeding lentils produced forage quality similar to 90 kg N ha-1. Inter-seeding grasspea into bermudagrass paddocks can produce sufficient forage in the spring to allow the initiation of grazing 30 d earlier than the traditional way of grazing bermudagrass in the southern Great Plains. Although additional studies are needed to optimize management for inter-seeded grasspea, this practice can improve the quality and alter the duration of available grazing for bermudagrass paddocks and reduce the input of chemical fertilizers.